IR spectroscopy measurements may be useful for a variety of purposes including aerospace, automotive and industrial applications, as well as biological and bio-medical applications. For example, infrared (IR) radiation is readily absorbed by materials in association with relative motions (vibrations) of atoms such as carbon, hydrogen, oxygen and nitrogen. As such, IR spectroscopy measurements may indicate a condition of a wide variety or organic as well as inorganic materials. For example, organic polymer materials such as resin-fiber composites may degrade over time due to a variety of reasons including heat or ultraviolet (UV) light exposure. Chemical degradation to a polymer structure may occur, thereby affecting the desired properties of the polymer structure including structural integrity such as strength of a composite or the adhesive properties of an adhesive. Near IR (1600-2400 nm) works well in testing thermal effect on resin rich materials but does not currently work on UV effect measurement. Only FT-IR (2.5 to 16.7 microns or 4000 to 600 wave numbers) works on UV effect and only FT-IR works on resin poor and fiber rich situations as in a composite repair where material is sanded away to leave a fiber rich resin poor surface.
Chemical degradation of a polymer material may be caused by exposure to normal environmental conditions over time, including normal temperature variations and ultra-violet light, as well as exposure to abnormal conditions such as elevated temperatures and stresses, resulting in oxidation and the breaking of existing polymer chemical bonds or forming of new polymer chemical bonds. Maintenance of polymeric materials requires a determination of the degree of degradation of the desirable properties, such as strength, of the polymeric material.
One non-destructive method of ascertaining the condition of polymeric containing material, such as the degree of heat effect to composite materials includes IR spectroscopy of the composite material as outlined in U.S. Pat. No. 7,113,869, which is hereby incorporated by reference in its entirety.
Other non-destructive methods in the prior art include using IR spectroscopy to determine the amount of a chromated conversion coating on a metallic substrate (U.S. Pat. No. 6,794,631), determining the amount of an anodize coating on a metallic substrate, (U.S. Pat. No. 6,784,431), determining and amount of opaque coating on a substrate (U.S. Pat. No. 6,903,339), and determining an amount of heat exposure to a resin-fiber composite substrate (U.S. Pat. No. 7,113,869), all of which are fully incorporated by reference herein.
However, in many cases, materials that could benefit from non-destructive IR spectroscopy, cannot be efficiently accessed within their normally existing operating environments by IR spectroscopy measurement methods and devices of the prior art, such as aircraft materials and parts where they must be accessed in the field by maintenance personnel to determine the acceptability of materials and parts and to aid in the repair of materials and parts. Prior methods used single absorbance band or dual absorbance bands methods and multivariate calibration with a broad band IR spectra make use of many absorbance bands and give more robust calibration and prediction results for composite material properties. Multivariate methods require careful sample preparation and in some cases proper sample fiber orientation for reproducible results with hand-held IR methods.
Thus, there is a continuing need for improved IR non-destructive testing devices and methods for performing IR spectroscopy measurements to non-destructively determine a physical property of surfaces of materials including composite fiber-resin materials.
Therefore it is an object of the disclosure to provide improved IR non-destructive testing devices and methods and to provide important sample preparation and sample orientation methods for performing IR spectroscopy measurements to non-destructively determine a physical property of surfaces of materials including composite fiber-resin materials present in operating configurations in the field, such as on aircraft.